record keeping

Get a software accounting system for your business (I use QuickBooks, there are a bunch of others out there) and let it do the work for recording your income.

Unless you own a studio with rents, heat, light, etc. that the business pays, expenses are even easier.  Set up a file for your expenses, and throw EVERY receipt in it.  If you're buying groceries, and you pick up a spiral notebook for use in your teaching, circle it on the receipt and throw it in the file.  Once a month, total up your receipts, put 'em in an envelope, and write the month and amount on the outside - all that stuff is tax deductable.  Plug it into the accounting system as 'deductable expenses' or just 'expenses'.  I date mine in the system as of the first of the month - you can use the last of the month as well.

Be sure to include the receipt for the accounting software too :)

If you travel to students, keep a mileage log: date, start miles, end miles, student name.  You can deduct mileage as well.

Just those steps will give you enough to satisfy the government, and the detailed receipts are easy enough to produce in case of an audit.  If you buy something that might be 'questionable' as a business expense, you might want to put a note right on the receipt as to why you needed it for the business... ink is the best memory I've found, and if you ever get audited it will help a lot.